Assign null to Variables That Are No Longer Needed

Explicitly
assigning a null value to variables that are no longer needed helps the garbage
collector to identify the parts of memory that can be safely reclaimed. Although
Java provides memory management, it does not prevent memory leaks or using
excessive amounts of memory.

An application may induce memory leaks by not releasing object references.
Doing so prevents the Java garbage collector from reclaiming those objects,
and results in increasing amounts of memory being used. Explicitly nullifying
references to variables after their use allows the garbage collector to reclaim
memory.

One way to detect memory leaks is to employ profiling tools and take
memory snapshots after each transaction. A leak-free application in steady
state will show a steady active heap memory after garbage collections.